This invention relates to the art of ice cube making machines, and, more particularly, to an improved control for ice making machines to automatically produce ice cubes over recurring cycles of freezing and harvesting.
Machines have been evolved which automatically produce ice cubes by going through sequential freezing and harvesting cycles. During the freezing cycle, the ice cubes are produced and during the harvesting cycle the cubes are discharged by the machine into a storage compartment. It is essential to operate such machines to accurately initiate and terminate the respective freezing and harvesting cycles to insure the formation of the desired cubes. To this end, a number of various control devices have been suggested for ice making machines.
Thus, in the machine disclosed in U.S. Pat. No. 3,009,336, a weight control is employed responsive to the weight of the water by-passed from the freezing chamber indicating that the chamber is full of ice, to initiate harvest.
Such previously evolved weight controls present problems in that the by-passed water is retained in a spring balanced pilot tank assembly which is relatively costly and requires excessive maintenance and adjustment.
Applicant, in his prior U.S. Pat. No. 3,277,661, attempted to eliminate the problems of the above described weight control by employing a thermostatic temperature responsive arrangement. However, in order to attain a desired mode of operation, it was necessary to employ two thermostats. One thermostat is responsive to a first relatively high temperature in the ice forming chamber indicative of the fact that there is no ice in the freezing chamber at which time the thermostat closes a switch to initiate the freezing cycle. The second thermostat is responsive to a given low temperature indicative of the fact that any water in the freezing chamber is frozen, at which time the thermostat closes a switch to initiate the harvest cycle. In applicant's prior patent, the first thermostat is disclosed as initiating the freezing cycle at a temperature of approximately 55.degree. F. and at a temperature of approximately 30.degree. F. acting to bring the second thermostat into the circuit. Thereafter, when the second thermostat senses a temperature of 10.degree. F., the second thermostat initiates the harvest cycle.
Though the use of thermostatic controls eliminates the problems with the weight control, it is found that with aging, and irregularities in the ambient atmosphere in which the ice making equipment is located, relatively extensive servicing of the equipment is required to adjust and maintain the setting of the thermostats to obtain desired freezing. Such servicing requires the skills of trained mechanics, and can generally not be performed by the equipment owner.
Additionally, it is found that even where given temperatures are attained, desired freezing does not necessarily occur due to variations in water turbulence, and the physical and chemical nature of the water, so that adjustment or replacement of the thermostat does not always alleviate the problem.